Electric motor actuators and their control circuits and devices produce heat that increases with their operating current, and they must thus be designed to operate within limits to prevent their being harmed by thermal overload. In the case of such electric motor actuators operating at substantially constant loads, this is a relatively straightforward task well known in the prior art. But many such electric motor actuators, particularly those used in vehicle systems, are subject to a wide range of loads for highly varying periods of time. For example, the electric actuating motor in a vehicle electric power steering system may require only 15 amps current for long periods of time but may require 75 amps current for shorter periods such as 5 seconds. A standard protection method for such a motor limits a motor control parameter such as motor operating current to the highest expected value (75 amps in the example). But, in the absence of a time specification, this requires the motor and control circuit to be designed to accommodate such loads for an indefinite time. Such a motor and control circuit is greatly over-designed for normal use and thus unacceptably expensive for a highly competitive market. It is also known to use thermal sensors such as thermistors to directly measure temperature in a current limiting system, but such sensors tend to be slow in response and difficult to place accurately.